A conventional four-point seat belt system for a seat of a vehicle includes two lap belts and two shoulder belts. A first lap belt extends upwardly from a first lap belt retractor mounted on a right side of the vehicle seat and is fixed to a first portion of a buckle assembly. A second lap belt extends upwardly from a second lap belt retractor mounted on a left side of the vehicle seat and is fixed to a second portion of the buckle assembly. A first shoulder belt extends from a first shoulder belt retractor downward to the first portion of the buckle assembly. A second shoulder belt extends from a second shoulder belt retractor downward to the second portion of the buckle assembly. The first and second portions of the buckle assembly latch together to secure the four-point seat belt system about an occupant of the seat.
When the four-point seat belt system is secured about the occupant, it is desirable to maintain the buckle assembly adjacent the top of the lap of the occupant. The positioning of the buckle assembly adjacent the top of the lap of the occupant helps to prevent the occupant from “submarining” or sliding forward on the cushion portion of the seat under the buckle assembly during the occurrence of a crash condition.
A conventional four-point seat belt system provides lap belt retractors with rewind springs that are stronger than the rewind springs of the shoulder belt retractors in order to position the buckle assembly adjacent the top of the occupant's lap. At the same time, however, the lap belt retractors must be positioned relative to the occupant to help to restrain the occupant in the seat in the event of a crash condition. The lap belt retractors are therefore generally positioned rearward of the lap of the occupant. As a result of the rearward positioning of the lap belt retractors, the rewind springs of the lap belt retractors tend to pull the buckle assembly both downward relative to the seat and rearward against the torso of the occupant. The rearward force of the buckle assembly against the torso of the occupant results in an increased frictional resistance to downward movement of the buckle assembly. As a result, the buckle assembly may become positioned away from the top of the lap of the occupant.